CN109079109B - Mould and method for casting thin-wall parts - Google Patents

Abstract

The present disclosure relates to a mold and a method for casting a thin-walled part, the mold comprises a first mold (1), a second mold (2), a male mold (11), a female mold (21), and a thermal expansion layer (3), wherein the male mold (11) is arranged on the first mold (1), the female mold (21) is arranged on the second mold (2), the male mold (11) and the female mold (21) cooperate to form a mold cavity, the thermal expansion layer (3) is arranged between the male mold (11) and the first mold (1), and when thermally expanded, the male mold (11) can be pushed towards the female mold (21) so as to reduce a gap between the male mold (11) and the female mold (21). The thickness of the die cavity in the die is larger than that of the thin-wall part, so that the pouring of the casting soup bases is convenient; on the other hand, the quality of the thin-wall parts cast by the die is high, and the rejection rate is low.

Description

Mould and method for casting thin-wall parts

Technical Field

The present disclosure relates to the field of mold casting, and in particular, to a mold and method for casting thin-walled parts.

Background

In the prior art, the idea of avoiding or compensating the thermal expansion of the mold is adopted, namely the mold expands when heated, which causes the size of the mold cavity to be increased, so that the size of the part is larger, therefore, the mold cavity is properly reduced during the mold design, and the size of the part is compensated.

However, with the annual increase of the requirement for light weight of automobiles, the thinner the wall thickness of the automobile casting, the difficulty in controlling the compensation design is high; meanwhile, the mold is heated and expanded in a gradual change process, when the initial mold cavity is small and is not expanded, the filled soup bases are difficult to fill the mold cavity smoothly, the casting effect is influenced, the casting quality is low, the precision is poor, and the rejection rate is high.

Disclosure of Invention

The first purpose of the present disclosure is to provide a mold for casting a thin-wall part, which can cast the thin-wall part, and improve the precision and quality of casting the thin-wall part and reduce the rejection rate.

A second object of the present disclosure is to provide a casting method of casting a thin-walled part, which is capable of casting a high-precision, high-quality thin-walled part.

In order to achieve the above object, the present disclosure provides a mold for casting a thin-walled part, wherein the mold comprises a first mold, a second mold, a male mold, a female mold, and a thermal expansion layer, the male mold is disposed on the first mold, the female mold is disposed on the second mold, the male mold and the female mold cooperate to form a mold cavity, and the thermal expansion layer is disposed between the male mold and the first mold, and can push the male mold towards the female mold when expanding under heat so as to reduce a gap between the male mold and the female mold.

Optionally, the first mold is a lower mold, the second mold is an upper mold, a groove is formed on an upper surface of the first mold, the thermal expansion layer is disposed in the groove, and the male mold is disposed on an upper surface of the thermal expansion layer.

Optionally, the die further comprises an annular sealing element, the annular sealing element is fixed to the first die, the outer ring of the annular sealing element is attached to the inner wall of the periphery of the groove body, the periphery of the male die is attached to the inner ring of the annular sealing element, and the periphery of the thermal expansion layer is attached to the inner ring of the annular sealing element.

Optionally, the mold further comprises a slag channel, wherein the slag channel is arranged on the first mold and used for discharging the redundant molten metal.

Optionally, the female die is formed integrally with the second mold.

Optionally, the material of the thermal expansion layer is low sulfur expanded graphite, polyethylene terephthalate, or rubber.

Optionally, the first mold, the second mold, the male mold and the female mold are sand core molds or solution molds, and a heating device for heating the thermal expansion layer is arranged in the first mold.

Optionally, the first mold is a moving mold, and the second mold is a static mold.

According to a second aspect of the present disclosure, there is also provided a method of casting a thin-walled part, the method comprising:

closing the die to enable the gap between the female die and the male die to be larger than the thickness required by the thin-wall part;

injecting molten metal into the die cavity from the female die, so that the thermal expansion layer is heated to expand to eject the male die, and the gap between the male die and the female die is reduced to the thickness required by the thin-wall part;

and opening the mold after the molten metal is cooled and formed in the mold cavity, and taking out the prepared casting.

Optionally, the casting pressure holding time is 1-10min, and the die opening time is 5-30 min.

The beneficial effect of this disclosure:

the thickness of the mold cavity is larger than that of the thin-wall part, so that the filling of the soup bases is facilitated. When the thermal expansion layer is heated and expanded, the male die can be pushed towards the direction of the female die, so that the gap between the male die and the female die is reduced, the thickness required by the thin-wall part can be reduced, the quality of the cast thin-wall part is improved, and the rejection rate is reduced.

Additional features and advantages of the disclosure will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure. In the drawings:

FIG. 1 is a schematic structural view of a mold for casting thin-walled parts according to an embodiment of the present disclosure;

FIG. 2 is an exploded view of the assembly of the mold shown in FIG. 1;

FIG. 3 is a schematic cross-sectional view of a second mold and a female mold of the mold shown in FIG. 1;

fig. 4 is a schematic sectional view of the first mold, the thermal expansion layer, the ring seal, and the male mold in the mold shown in fig. 1.

Description of the reference numerals

1 first mould 2 second mould

3 thermal expansion layer 4 annular seal

11 terrace dies of 5 slag ways

12 groove 21 die

6 thin-walled part

Detailed Description

The following detailed description of specific embodiments of the present disclosure is provided in connection with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.

As shown in fig. 1 to 4, the present disclosure provides a mold for casting a thin-walled part, the mold includes a first mold 1, a second mold 2, a male mold 11, a female mold 21, and a thermal expansion layer 3, the male mold 11 is disposed on the first mold 1, the female mold 21 is disposed on the second mold 2, the male mold 11 and the female mold 21 cooperate to form a mold cavity, the thermal expansion layer 3 is disposed between the male mold 11 and the first mold 1, and the male mold 11 can be pushed toward the female mold 21 when expanding by heat, so as to reduce a gap between the male mold 11 and the female mold 21.

Wherein, when the first mold 1 and the second mold 2 are closed, a certain gap is left between the upper end of the first mold 1 and the lower end of the second mold 2, in order to make it possible for the male mold 11 to move toward the female mold 21 when the thermal expansion layer 3 is thermally expanded. The male die 11 arranged on the first die 1 and the female die 21 arranged on the second die 2 are matched to form a die cavity, the thickness of the die cavity is the gap between the male die 11 and the female die 21 (the gap is 6-12mm, and the gaps in different regions can be the same or different), and the thickness of the die cavity is larger than the thickness of the thin-wall part to be cast (the thickness of the cast thin-wall part is 0.5-6mm, preferably 1-4mm, more preferably 1.5mm-2.5mm), so that the pouring of the molten metal is more convenient. When molten metal is poured into the cavity of the mold (the temperature of the molten metal is set to be 50-400 ℃ higher than the melting point of the metal, and is preferably 80-300 ℃), the male mold 11 transfers the heat of the molten metal to the thermal expansion layer 3, the thermal expansion layer 3 is heated to expand, so that the male mold 11 is pushed towards the female mold 21, and the gap between the male mold 11 and the female mold 21 is further reduced, and the reduced gap is 0.5-6mm, preferably 1-4mm, and more preferably 1.5-2.5 mm. The molten metal can be extruded to obtain the thin-wall part 6 with the thickness meeting the requirement, the quality of the cast thin-wall part 6 is improved, and the rejection rate is reduced.

In an alternative embodiment, as shown in fig. 2, 3 and 4, the first mold 1 is a lower mold, the second mold 2 is an upper mold, a groove 12 is formed on an upper surface of the first mold 1, the thermal expansion layer 3 is disposed in the groove 12, and the male mold 11 is placed on the upper surface of the thermal expansion layer 3. Set up first mould 1 into the bed die, second mould 2 sets up to the mould, and the lower extreme of mould cavity is flowed to from the upper end of mould cavity to the pouring of metal liquid, adopts such arrangement mode can make the metal liquid down move under the effect of self gravity, makes things convenient for pouring of metal liquid more. A groove body 12 is formed on the upper surface of the first mold 1, the thermal expansion layer 3 is disposed in the groove body 12, and a male mold 11 is disposed on the upper surface of the thermal expansion layer 3, so that the male mold 11 can move toward the female mold 21 by the thermal expansion layer 3.

In the present disclosure, as shown in fig. 2, 3 and 4, the mold further includes an annular sealing member 4, the annular sealing member 4 is fixed to the first mold 1, an outer ring of the annular sealing member 4 is attached to an inner wall of the periphery of the groove body 12, the periphery of the male mold 11 is attached to an inner ring of the annular sealing member 4, and the periphery of the thermal expansion layer 3 is attached to the inner ring of the annular sealing member 4. Specifically, the annular seal member 4 may be a self-lubricating sealing material, which may be an engineering plastic such as polytetrafluoroethylene, polyacetal, polyoxymethylene, polycarbonate, polyamide, polysulfone, polyimide, chlorinated polyether, polyphenylene sulfide, and polyester terephthalate; these engineering plastics may be reinforced composite materials such as glass fibers, metal fibers, graphite fibers, and boron, or graphite, silicon nitride, and the like may be used on the surface of these materials to enhance the lubricating effect. The annular sealing element 4 is fixed on the first mold 1, and more specifically, the annular sealing element 4 may be fixedly disposed in the groove body 12, and an outer ring of the annular sealing element 4 is attached to a peripheral inner wall of the groove body 12. As an alternative embodiment, the annular sealing element 4 is fixed on the circumferential inner wall of the groove body 12 through an outer ring, so as to achieve the fixing effect. The periphery of the lower end of the male die 11 is attached to the inner ring of the annular sealing element 4. When the thermal expansion layer 3 expands due to heat and pushes the male die 11 out towards the female die 21, the thermal expansion layer 3 and the male die 11 move towards the female die 21 in the inner ring of the annular sealing element 4, and the annular sealing element 4 is fixed. In addition, when the molten metal is poured, the molten metal flows to the thermal expansion layer 3 along the inner wall of the groove body 12, so that the thermal expansion layer 3 is damaged, the annular sealing piece 4 is arranged, the damage of the molten metal to the thermal expansion layer 3 can be effectively reduced, and the service life is prolonged.

As shown in fig. 2, the mold further includes a slag channel 5, and the slag channel 5 is disposed on the first mold 1 and used for discharging the excessive molten metal. In an alternative embodiment, 4 runners 5 are provided on the upper surface of the first mould 1 to facilitate the removal of excess molten metal.

In an alternative embodiment, the concave die 21 is formed integrally with the second mold 2, specifically, the concave die 21 is formed in the second mold 2, and this arrangement can effectively reduce unnecessary parts and reduce the cost.

Specifically, the material of the thermal expansion layer 3 is a heat-sensitive high-temperature resistant thermal expansion material such as low-sulfur expanded graphite, polyethylene terephthalate, or rubber, and the like, and low-sulfur expanded graphite or the like is commonly used, and when the material is cast at a low temperature, a material such as polyethylene terephthalate, polystyrene, or rubber may be used. Furthermore, the thermal expansion coefficient of the thermal expansion layer 3 is much higher than that of the material of the mold itself (including the first mold 1, the second mold 2, the male mold 11, and the female mold 21), that is, the volume change amount of the mold itself is much smaller than that of the thermal expansion layer 3.

As an optional implementation manner, the first mold 1, the second mold 2, the male mold 11, and the female mold 21 are steel molds, and the steel molds have high heat conductivity, so that when the steel molds are used as the molds, after the molten metal is injected into the molds, the heat of the molten metal can be effectively transferred to the thermal expansion layer 3 through the steel molds, and the expansion speed of the thermal expansion layer is ensured.

As another alternative embodiment, the first mold 1, the second mold 2, the male mold 11, and the female mold 21 are sand core molds or solution molds, and the first mold 1 is provided with a heating device for heating the thermal expansion layer 3, because the cost of the sand core molds or solution molds is lower than that of the steel molds, the sand core molds or solution molds are frequently used in practical production, but their thermal conductivity is poor, so when the sand core molds or solution molds are used as the molds, the heating device is provided in the first mold 1 to increase the expansion speed of the thermal expansion layer 3 and ensure the accuracy of the expansion amount of the thermal expansion layer 3.

In the present disclosure, the first mold 1 is a moving mold, and the second mold 2 is a stationary mold. Before first mould 1 and second mould 2 have not closed yet, second mould 2 is the stationary mould, and first mould 1 is the mould that moves, and first mould 1 moves to the position of second mould 2, realizes closed effect. As an alternative embodiment, the first mold 1 may be a static mold, and the second mold 2 may be a static mold, which may also achieve the closing effect.

According to a second aspect of the present disclosure, there is also provided a method of casting a thin-walled part, the method comprising:

closing the die, so that the gap between the female die 21 and the male die 11 is larger than the thickness required by the thin-wall part;

injecting molten metal into a mold cavity from a female mold 21, enabling the thermal expansion layer 3 to expand under heat so as to eject the male mold 11, and enabling a gap between the male mold 11 and the female mold 21 to be reduced to the thickness required by the thin-wall part;

and after the molten metal is cooled and formed in the die cavity of the die, opening the die and taking out the prepared casting.

Specifically, when a heating device is arranged in the first mold 1, the temperature of the mold can be controlled by controlling the heating device, so that the variation of the gap between the male mold 11 and the female mold 21 can be controlled, and thin-wall parts with different thicknesses can be cast. The specific principle is as follows: the initial filling thickness L0 of the thermal expansion layer 3 is obtained, the initial thickness of the mold cavity is defined as L1, the final thickness of the mold cavity is defined as L2, T is defined as the heat preservation temperature of the mold during casting, T0 is defined as the initial temperature of the thermal expansion layer 3, and alpha is defined as the thermal expansion coefficient of the thermal expansion layer 3, a formula T0+ (L1-L2)/alpha L0 can be obtained, in the formula, the thickness of L2 is the thickness of the thin-wall part to be cast, when the thin-wall parts with different thicknesses need to be cast, the heat preservation temperature T of the mold can be controlled by controlling a heating device, and the purpose of casting the thin-wall parts with different thicknesses is achieved.

In the disclosure, the pressure holding time of casting is 1-10min, and the die opening time is 5-30 min. Specifically, the holding pressure time refers to the time of continuously injecting molten metal into the mold, the mold opening time refers to the time from the end of molten metal injection to the opening of the mold, and the prepared casting is taken out after the mold is opened, wherein the porosity of the casting is less than 5%. And then, the taken casting can be subjected to post-treatment such as cutting, polishing, coating and the like, so that the thin-wall part meeting the requirement can be obtained.

The thin-wall part can be a thin-wall part of a vehicle body, which is used for parts of automobile structural parts, covering parts and the like, the thin-wall part of the vehicle body comprises but is not limited to aluminum alloy, magnesium alloy, gray cast iron, nodular cast iron, malleable cast iron, cast steel, brass, tin bronze, tin-free bronze, lead and the like, the casting process comprises but is not limited to gravity casting, low-pressure casting, high-pressure casting, centrifugal casting, differential pressure casting and the like, and the casting mold comprises but is not limited to steel mold, sand mold, wax mold, ceramic mold, resin mold.

In order to meet the aim of light weight, light weight materials such as aluminum alloy and magnesium alloy are frequently selected for the conventional automobile castings. According to statistics, the wall thickness of 2-4mm can meet the performance requirements of most automobile parts, but when the traditional casting process is used, the resistance is large when molten metal flows between pores of 2-4mm, the filling is difficult, and bubbles are easily mixed; and the bubbles in the casting expand when heated, so that the parts are damaged. In the whole vehicle assembly process, the connection modes such as welding, riveting and the like are usually involved, and the welding temperature needs to exceed the metal melting point (the melting point of aluminum alloy and magnesium alloy is about 500-700 ℃, and the melting point of steel is 1500 ℃); although the riveting process temperature is not high, the elongation rate of the material is required to be higher than 12%, and the material such as aluminum alloy, magnesium alloy and the like can be achieved only by high-temperature heat treatment, so that parts containing air bubbles cannot meet the requirements of the whole vehicle assembly process.

In the traditional casting process, the thickness of parts is increased (for example, the parts are thickened to 6-8mm by sand casting), and the lightweight effect is sacrificed; or adopt high vacuum die casting technology, promote die stamping efficiency through the mode of evacuation, reduce gaseous inclusion, nevertheless need dedicated evacuation equipment, and can only use the steel mould, with high costs, the development cycle is long, can't satisfy the new generation rhythm demand of modern motorcycle type.

The casting method disclosed by the invention can adopt a common casting process, so that simple molds such as a sand core mold and a soluble mold can be used, the development period is short, the cost is low, and the application of thin-walled cast parts in the automobile industry can be effectively improved.

The preferred embodiments of the present disclosure are described in detail with reference to the accompanying drawings, however, the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present disclosure within the technical idea of the present disclosure, and these simple modifications all belong to the protection scope of the present disclosure. It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various combinations that are possible in the present disclosure are not described again.

In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.

Claims (8)

1. A mould for casting thin-walled parts, characterized in that the mould comprises a first mould (1), a second mould (2), a male mould (11), a female mould (21), a thermal expansion layer (3), wherein the male mould (11) is arranged on the first mould (1), the female mould (21) is arranged on the second mould (2), the male mould (11) and the female mould (21) are matched to form a mould cavity, the thermal expansion layer (3) is arranged between the male mould (11) and the first mould (1) and can push the male mould (11) towards the female mould (21) when expanding under heat so as to reduce the gap between the male mould (11) and the female mould (21),

the first die (1) is a lower die, the second die (2) is an upper die, a groove body (12) is formed on the upper surface of the first die (1), the thermal expansion layer (3) is arranged in the groove body (12), the convex die (11) is placed on the upper surface of the thermal expansion layer (3),

the mould still includes annular seal spare (4), annular seal spare (4) are fixed in first mould (1), just the outer lane of annular seal spare (4) with inner wall laminating all around of cell body (12), terrace die (11) all around with the inner circle laminating of annular seal spare (4), thermal expansion layer (3) all around with the inner circle laminating of annular seal spare (4).

2. Mould for casting thin-walled parts according to claim 1, characterized in that the mould further comprises a slag channel (5), which slag channel (5) is arranged on the first mould (1) for draining excess molten metal.

3. Mould for casting thin-walled parts according to claim 1, characterized in that the female mould (21) is formed in one piece with the second mould (2).

4. Mould for casting thin-walled parts according to claim 1, characterized in that the material of the thermal expansion layer (3) is low-sulphur expanded graphite, polyethylene terephthalate or rubber.

5. The die for casting the thin-wall part according to claim 1, wherein the first die (1), the second die (2), the male die (11) and the female die (21) are sand core dies or solvent dies, and a heating device for heating the thermal expansion layer (3) is arranged in the first die (1).

6. Mould for casting thin-walled parts according to any of claims 1 to 5, characterized in that the first mould (1) is a moving mould and the second mould (2) is a static mould.

7. A method of casting a thin-walled part using the mold of any of claims 1-6, the method comprising:

closing the die to enable the gap between the female die (21) and the male die (11) to be larger than the thickness required by the thin-wall part;

injecting molten metal into the die cavity from the female die (21), heating and expanding the thermal expansion layer (3) to eject the male die (11), and reducing the gap between the male die (11) and the female die (21) to the thickness required by the thin-wall part;

and opening the mold after the molten metal is cooled and formed in the mold cavity, and taking out the prepared casting.

8. The method of casting thin-walled parts according to claim 7, wherein the holding time for casting is 1 to 10min and the open time is 5 to 30 min.

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